COLUMBIA, Md.--(BUSINESS WIRE)--Jul 2, 2012 -
Osiris Therapeutics, Inc. (NASDAQ: OSIR), announced today
interim one-year results from its groundbreaking clinical trial
evaluating Prochymal® (remestemcel-L) for the treatment
of patients experiencing first-time acute myocardial infarction.
The trial is the largest study of allogeneic or "off-the-shelf"
stem cells ever conducted in heart attack patients. A total of 220
patients were given a single infusion of either Prochymal or
placebo through a standard intravenous line within seven days of an
acute heart attack.

Cardiac MRI assessments were conducted for six months following
infarct to evaluate cardiac remodeling. Patients receiving
Prochymal had significantly less cardiac hypertrophy, as measured
by cardiac MRI, compared to patients receiving placebo (p<0.05).
Patients treated with Prochymal also experienced significantly less
stress-induced ventricular arrhythmia (p<0.05). Cardiac
hypertrophy and ventricular arrhythmia are indicators of
pathological remodeling following heart injury and provide insight
into the mechanism by which mesenchymal stem cells attenuate heart
injury following a myocardial infarction.

The mechanistic data is complemented by clinical data showing
treatment with Prochymal resulted in a statistically significant
reduction in heart failure. In the study, seven patients who were
treated with placebo have progressed to heart failure requiring
treatment with intravenous diuretics, compared to none of the
Prochymal patients (p=0.01). Furthermore, patients receiving
placebo tended to require re-hospitalization for cardiac issues
sooner than the patients receiving Prochymal (median 27.5 days vs.
85.5 days).

“This study is the largest of its kind and provides key
insights into the mechanism of action of mesenchymal stem cells in
the setting of acute myocardial infarction,” said Lode
Debrabandere, Ph.D., Senior Vice President of Therapeutics at
Osiris. “These important mechanistic observations are
consistent with data obtained from our preclinical models and from
the first placebo-controlled human trial with Prochymal published
in the Journal of the American College of Cardiology. Given the
quality of the data and highly encouraging results observed thus
far, we are extending the trial's duration to capture a better
understanding of the long-term clinical benefits of MSCs."

The trial also demonstrated that treatment with Prochymal was
safe. There were no infusional toxicities observed in patients
receiving Prochymal. Serious adverse events occurred with equal
frequency in both treatment groups (31.8%). To date, there have
been 5 deaths in the trial, 2 in the Prochymal group and 3 in the
placebo group.

“For interventional cardiologists, keeping our myocardial
infarction patients from progressing to heart failure is central to
our mission,” said Mark Vesely, M.D., Principal Investigator
on the Study and Assistant Professor of Medicine (Interventional
Cardiology) at the University of Maryland School of Medicine.
“It is remarkable and very encouraging to see significant
changes in clinically meaningful parameters this early in the
study. We look forward to the additional data that will be gathered
as the study progresses, which will help us to better understand
both the magnitude and durability of the benefit to
treatment.”

Prochymal, the world's first and only stem cell drug approved by
an internationally recognized regulatory authority, is used for the
treatment of graft vs. host disease (GvHD). GvHD is a devastating
complication of bone marrow transplantation that kills up to 80
percent of children affected. Prochymal is now approved in Canada
and New Zealand, and is currently available in seven other
countries including the United States under an Expanded Access
Program (EAP).

About the Trial

This Phase 2, multi-center, randomized, double-blind,
placebo-controlled study is evaluating the safety and efficacy of
Prochymal (ex-vivo cultured adult human mesenchymal stem
cells) intravenous infusion following acute myocardial infarction.
A total of 220 patients were randomized (1:1) at 33 centers in the
United States and Canada and received a single intravenous infusion
of Prochymal or placebo within 7 days following first acute
myocardial infarction. In addition to screening and baseline visits
prior to the infusion, initially follow-up evaluations were
scheduled to be conducted through 2 years. Given the encouraging
results observed at the one year time-point, the trial is being
extended to include 5 years of follow-up. Both male and female
subjects between 21 and 85 years of age were enrolled. Patients had
to have a left ventricular ejection fraction (LVEF) between 20% and
45% as determined by quantitative echocardiography or cardiac MRI
at least 24 hours after successful reperfusion of the culprit
vessel. In addition, troponin levels must have been greater than 4
times the upper limit of normal during the first 72 hours of
hospitalization for the MI.

About Prochymal (remestemcel-L)

Prochymal is the world's first approved drug with a stem cell as
its active ingredient. Developed by Osiris Therapeutics, Prochymal
is an intravenous formulation of MSCs, which are derived from the
bone marrow of healthy adult donors between the ages of 18 and 30
years. The MSCs are selected from the bone marrow and grown in
culture so that up to 10,000 doses of Prochymal can be produced
from a single donor. Prochymal is truly an off-the-shelf stem cell
product that is stored frozen at the point-of-care and infused
through a simple intravenous line without the need to type or
immunosuppress the recipient. Prochymal is approved in Canada and
New Zealand for the management of acute graft-versus-host disease
(GvHD) in children and is available for adults and children in
eight countries including the United States, under an Expanded
Access Program. Prochymal is currently in a Phase 3 trial for
refractory Crohn's disease and is also being evaluated in clinical
trials for the treatment of myocardial infarction (heart attack)
and type 1 diabetes.

About Osiris Therapeutics

Osiris Therapeutics, Inc. is the leading stem cell company,
having developed the world's first approved stem cell drug,
Prochymal. The company is focused on developing and marketing
products to treat medical conditions in inflammatory,
cardiovascular, orthopedic and wound healing markets. In
Biosurgery, Osiris currently markets Grafix® for burns and
chronic wounds, and Ovation® for orthopedic applications.
Osiris is a fully integrated company with capabilities in research,
development, manufacturing and distribution of stem cell products.
Osiris has developed an extensive intellectual property portfolio
to protect the company's technology, including 48 U.S. and 144
foreign patents.

Osiris, Prochymal, Grafix and Ovation are registered trademarks
of Osiris Therapeutics, Inc. More information can be found on the
company's website,
www.Osiris.com. (OSIR?G)

Forward-Looking Statements

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product candidates in development; status of the regulatory process
for our biologic drug candidates; implementation of our corporate
strategy; our financial performance; our product research and
development activities and projected expenditures, including our
anticipated timeline and clinical strategy for Prochymal,
Chondrogen and our other MSC and biologic drug candidates; our cash
needs; patents and proprietary rights; the safety and ability of
our potential products to treat disease and the results of our
scientific research; our plans for sales and marketing; our plans
regarding our facilities; types of regulatory frameworks we expect
will be applicable to our potential products; and results of our
scientific research. Forward-looking statements are subject to
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